To limit or remedy environmental damage, a problem often recurring in practice is the removal of liquid pollutants such as hydrocarbons which have entered the ground, in order to decontaminate the groundwater. For this purpose, a variety of decontamination methods are known which, however, are all very complex and costly.
In a known method (German published patent application DE-OS 3,721,981), groundwater is drawn from the ground, treated biologically above ground and subsequently returned to the ground, with a flushing stream being produced in the ground causing pollutant discharge. This known method has the disadvantage that removal of the pollutants is effected only indirectly through the flushing stream in dissolved or suspended form, so that large amounts of groundwater have to be pumped up for pollutant removal. As a consequence, the method is time-consuming and costly. It is a further disadvantage of the known method that it necessitates a separation or treatment plant above ground in order to separate the pollutants pumped up together with the water.